For certain applications, such as manpack transceivers that communicate with each other through a very low power, high noise transmission link, such as a link through a geo-stationary, synchronous satellite, it is necessary to provide a relatively simple, practical and reliable system for transmitting digital signalling messages. In such a transmission link, a message structure between the transceivers must be capable of reliable recognition of a true message, of low misinterpretation probability (incorrect message) and very low false recognition probability of random or unrelated messages or noise. While many structures have been designed to meet such requirement, few of the prior art structures lend themselves to simple, practical, low power and low cost decoding. It is very desirable for the message structure to provide automatic word synchronization, as well as high immunity to word timing errors with simple circuitry. It is also necessary for the link and system to enable binary data to be recognized correctly, even though a significant percentage of the message bits are erroneously received due to link perturbations or high ambient noise.
A particular application where such data transmission is necessary involves selectively calling one of several transceivers from a single transmitter or simultaneous calling of several transceivers from a single transmitter. Each called transceiver is assigned a number, which can be represented as a series of binary bits. We are aware of no prior art structures or communication links which are capable of meeting all of the requirements required to address one of several stations with the stated performance criteria.